OBJECTIVES

2. OBJECTIVES After studying Chapter 11, the reader will be able to: • Describe how the proper grade of gasoline affects engine performance. • List gasoline purchasing hints. • Discuss how volatility affects driveability. • Explain how oxygenated fuels can reduce CO exhaust emissions. • Discuss the advantages and disadvantages of various alternative fuels.

3. AUTOMOTIVE FUEL REFINING • As it comes out of the ground, petroleum (meaning “rock oil”) crude can be as thin and light colored as apple cider or as thick and black as melted tar.

4. AUTOMOTIVE FUEL REFININGProcesses • Refining is a complex combination of interdependent processing units, and it all starts with the simple physical separation process called distillation.

5. AUTOMOTIVE FUEL REFININGDistillation • In the late 1800s, crude was separated into different products by boiling. • Distillation works because crude is composed of hydrocarbons with a wide range of molecular weights, and therefore a broad range of boiling points.

6. AUTOMOTIVE FUEL REFININGCracking • Thermal cracking, was used to increase gasoline production starting in 1913. • It is the nature of thermal cracking to make a lot of olefins, which have higher octane numbers but may cause engine deposits. • Eventually heat was supplemented by a catalyst, transforming thermal cracking into catalytic cracking.

7. AUTOMOTIVE FUEL REFININGCracking FIGURE 11-1 The crude oil refining process showing most of the major steps and processes.

8. AUTOMOTIVE FUEL REFININGShipping • The gasoline is transported to regional storage facilities by tank railway car or by pipeline. • In the pipeline method, all gasoline from many refiners is often sent through the same pipeline and can become mixed.

9. GASOLINE • Gasoline is a term used to describe a complex mixture of various hydrocarbons refined from crude petroleum oil for use as a fuel in spark-ignition engines. • Most gasoline is “blended” to meet the needs of the local climates and altitudes.

10. VOLATILITY • Volatility describes how easily the gasoline evaporates (forms a vapor).

11. VOLATILITYWinter Blend • Reid vapor pressure (RVP) is the pressure of the vapor above the fuel when the fuel is at 100°F (38°C). • Increased vapor pressure permits the engine to start in cold weather. • Cold temperatures reduce the normal vaporization of gasoline; therefore, winterblended gasoline is specially formulated to vaporize at lower temperatures for proper starting and driveability at low ambient temperatures.

12. VOLATILITYSummer Blend • The volatility of summer-grade gasoline should be about 7.0 PSI RVP. • According to ASTM standards, the maximum RVP should be 10.5 PSI for summer-blend gasoline.

13. WHAT IS A CALIFORNIA GAS CAN? FIGURE 11-2 A gas can that meets the California Resources Board (CARB) approval uses a spring-loaded sealed nozzle that eliminates gasoline spillage and leaks into the atmosphere.

14. VOLATILITYVolatility Problems • At higher temperatures, liquid gasoline can easily vaporize, which can cause vapor lock. • If winter-blend gasoline (or high-RVP fuel) is used in an engine during warm weather, the following problems may occur: • Rough idle • Stalling • Hesitation on acceleration • Surging

15. VOLATILITYVolatility Problems FIGURE 11-3 A gasoline testing kit. Included is an insulated container where water at 100°F is used to heat a container holding a small sample of gasoline. The reading on the pressure gauge is the Reid vapor pressure (RVP).

16. DISTILLATION CURVE • Besides Reid vapor pressure, another method of classifying gasoline volatility is the distillation curve. • A curve on a graph is created by plotting the temperature at which the various percentage of the fuel evaporates.

17. DISTILLATION CURVE FIGURE 11-4 A typical distillation curve. Heavier molecules evaporate at higher temperatures and contain more heat energy for power, whereas the lighter molecules evaporate easier for starting.

18. DRIVEABILITY INDEX • A distillation curve shows how much of a gasoline evaporates at what temperature range. • To predict cold-weather driveability, an index was created called the driveability index, also called the distillation index, and abbreviated DI. • The formula for DI is: • DI = 1.5 x T10 + 3 x T50 + T90

19. NORMAL AND ABNORMAL COMBUSTION • The octane rating of gasoline is the measure of its antiknock properties. • Normal combustion occurs smoothly and progresses across the combustion chamber from the point of ignition. FIGURE 11-5 Normal combustion is a smooth, controlled burning of the air–fuel mixture.

20. NORMAL AND ABNORMAL COMBUSTION • During periods of spark knock (detonation), the combustion speed increases by up to 10 times to near the speed of sound. • The increased combustion speed also causes increased temperatures and pressures, which can damage pistons, gaskets, and cylinder heads FIGURE 11-6 Detonation is a secondary ignition of the air–fuel mixture. It is also called spark knock or pinging.

21. OCTANE RATING • The antiknock standard or basis of comparison was the knockresistant hydrocarbon isooctane, chemically called trimethylpentane (C8H18), also known as 2-2-4 trimethylpentane. • If a gasoline tested had the exact same antiknock characteristics as isooctane, it was rated as 100-octane gasoline. If the gasoline tested had only 85% of the antiknock properties of isooctane, it was rated as 85 octane.

22. GASOLINE GRADES AND OCTANE NUMBER • The posted octane rating on gasoline pumps is the rating achieved by the average of the research and the motor methods.

23. GASOLINE GRADES AND OCTANE NUMBER FIGURE 11-7 A typical fuel pump showing regular (87 octane), midgrade (89 octane), and premium (92 octane). These ratings can vary with brand as well as in different parts of the country, especially in high-altitude areas where the ratings are lower.

24. OCTANE IMPROVERS • When gasoline companies, under federal EPA regulations, removed tetraethyl lead from gasoline, other methods were developed to help maintain the antiknock properties of gasoline. • Octane improvers (enhancers) can be grouped into three broad categories: • Aromatic hydrocarbons • Alcohols such as ethanol • Metallic compounds

25. OXYGENATED FUELS • Oxygenated fuels contain oxygen in the molecule of the fuel itself.

26. OXYGENATED FUELSMethyl Tertiary Butyl Ether (MTBE) • MTBE is manufactured by means of the chemical reaction of methanol and isobutylene. • Unlike methanol, MTBE does not increase the volatility of the fuel, and is not as sensitive to water as are other alcohols.

27. OXYGENATED FUELSTertiary-Amyl Methyl Ether • Tertiary-amyl methyl ether (TAME) is an oxygenate added to gasoline and is flammable and can form explosive mixtures with air. • It is slightly soluble in water, very soluble in ethers and alcohol, and soluble in most organic solvents including hydrocarbons.

28. OXYGENATED FUELSEthyl Tertiary Butyl Ether • ETBE is derived from ethanol. • The maximum allowable volume level is 17.2%. • The use of ETBE is the cause of much of the odor from the exhaust of vehicles using reformulated gasoline.

29. OXYGENATED FUELSEthanol • Ethyl alcohol is drinkable alcohol and is usually made from grain. • Adding 10% ethanol (ethyl alcohol or grain alcohol) increases the (R + M) / 2 octane rating by three points. FIGURE 11-8 This fuel pump indicates that the gasoline is blended with 10% ethanol (ethyl alcohol) and can be used in any gasoline vehicle. E85 contains 85% ethanol and can only be used in vehicles specifically designed to use it.

30. OXYGENATED FUELSMethanol • Methyl alcohol is made from wood (wood alcohol), natural gas, or coal. • Methanol contains oxygen and gasoline containing 5% methanol would have an oxygen content of 2.5% by weight.

31. OXYGENATED FUELSMethanol FIGURE 11-9 A container with gasoline containing alcohol. Notice the separation line where the alcohol–water mixture separated from the gasoline and sank to the bottom.

32. ALCOHOL ADDITIVES—ADVANTAGES AND DISADVANTAGES • Advantages • Alcohol absorbs moisture in the fuel tank. • Ten percent alcohol added to gasoline raises the octane rating, (R M) 2, by three points. • Alcohol cleans the fuel system. • Alcohol reducesCOemissions because it contains oxygen.

33. ALCOHOL ADDITIVES—ADVANTAGES AND DISADVANTAGES • Disadvantages • The use of alcohol can result in the clogging of fuel filters with dirt and other debris cleaned from the fuel tank, pump, and lines. • Alcohol raises the volatility of fuel about 0.5 PSI; this can cause hot-weather driveability problems. • Alcohol reduces the heat content of the resulting fuel mixture (it has about one-half of the energy content of gasoline)—60,000 to 75,000 British thermal units (BTUs) per gallon for alcohol versus about 130,000 BTUs per gallon for gasoline. • Alcohol absorbs water and then separates from the gasoline, especially as temperature drops. Separated alcohol and water on the bottom of the tank can cause hard starting during cold weather. Alcohol does not vaporize easily fat low temperatures.

34. COMBUSTION CHEMISTRY • Internal combustion engines burn an organic fuel to produce power. • The term organic refers to a product (gasoline) from a source that originally was alive. FIGURE 11-10 An engine will not run if the air–fuel mixture is either too rich or too lean.

35. AIR–FUEL RATIOS • Fuel burns best when the intake system turns it into a fine spray and mixes it with air before sending it into the cylinders. • In fuel-injected engines, the fuel becomes a spray and mixes with the air in the intake manifold.

36. AIR–FUEL RATIOS • The air–fuel ratio is the proportion by weight of air and gasoline that the injection system mixes as needed for engine combustion. • These ratios are usually stated by weight, such as: • 8 parts of air by weight combined with 1 part of gasoline by weight (8:1), which is the richest mixture that an engine can tolerate and still fire reliably. • 18.5 parts of air mixed with 1 part of gasoline (18.5:1), which is the leanest practical ratio. Richer or leaner air–fuel ratios cause the engine to misfire badly or not run at all.

37. AIR–FUEL RATIOSStoichiometric Air–Fuel Ratio • The ideal mixture or ratio at which all of the fuel combines with all of the oxygen in the air and burns completely is called the stoichiometric ratio, a chemically perfect combination. FIGURE 11-11 With a three-way catalytic converter, emission control is most efficient with an air–fuel ratio between 14.65:1 and 14.75:1.

38. AIR–FUEL RATIOSStoichiometric Air–Fuel Ratio for Various Fuels • If the combustion process is complete, all gasoline or HCs will be completely combined with all the available oxygen. • This total combination of all components of the fuel is called stoichiometric air–fuel ratio.

39. HIGH-ALTITUDE OCTANE REQUIREMENTS • As the altitude increases, atmospheric pressure drops. • The air is less dense because a pound of air takes more volume. • The octane rating of fuel does not need to be as high because the engine cannot take in as much air. • This process will reduce the combustion (compression) pressures inside the engine.

40. HIGH-ALTITUDE OCTANE REQUIREMENTS FIGURE 11-12 Photo of gasoline pump taken in a high-altitude area. Note the lower-than-normal octane ratings. The “ethanol” sticker reads that all grades contain 10% ethanol from November 1 through February 28 each year to help reduce CO exhaust emissions.

41. REFORMULATED GASOLINE • Reformulated gasoline (RFG) is manufactured by refiners to help reduce emissions. • The gasoline refiners reformulate gasoline by using additives that contain at least 2% oxygen by weight and reducing the additive benzene to a maximum of 1% by volume. • Two other major changes done at the refineries are as follows: • Reduce light compounds. • Reduce heavy compounds.

42. WHAT IS “TOP-TIER”GASOLINE? • Top-tier gasoline is gasoline that has specific standards for quality, including enough detergent to keep all intake valves clean. • The gasoline companies that agreed to make fuel that matches or exceeds the standards as a top-tier fuel include Chevron Texaco and Conoco Phillips. FIGURE 11-13 The gas cap on a Ford vehicle notes that BP fuel is recommended.

43. GENERAL GASOLINE RECOMMENDATIONS • To help ensure proper engine operation and keep fuel costs to a minimum, follow these guidelines: • Purchase fuel from a busy station to help ensure that it is fresh and less likely to be contaminated with water or moisture. • Keep the fuel tank above one-quarter full, especially during seasons in which the temperature rises and falls by more than 20°F between daytime highs and nighttime lows.

44. GENERAL GASOLINE RECOMMENDATIONS • Do not purchase fuel with a higher octane rating than is necessary. • Avoid using gasoline with alcohol in warm weather, even though many alcohol blends do not affect engine driveability. • Do not purchase fuel from a retail outlet when a tanker truck is filling the underground tanks. • Do not overfill the gas tank. • Be careful when filling gasoline containers.

45. GENERAL GASOLINE RECOMMENDATIONS FIGURE 11-14 Many gasoline service stations have signs posted warning customers to place plastic fuel containers on the ground while filling. If placed in a trunk or pickup truck bed equipped with a plastic liner, static electricity could build up during fueling and discharge from the container to the metal nozzle, creating a spark and possible explosion. Some service stations have warning signs not to use cell phones while fueling to help avoid the possibility of an accidental spark creating a fire hazard.

46. ALTERNATIVE FUELS • Alternative fuels include a number of fuels besides gasoline for use in passenger vehicles. FIGURE 11-15 Some retail stations offer a variety of fuel choices, such as this station in Ohio where biodiesel, E10, and E85 are available.

47. ALTERNATIVE FUELSEthanol • Ethanol is also called ethyl alcohol or grain alcohol, because it is usually made from grain and is the type of alcohol found in alcoholic drinks such as beer, wine, and distilled spirits like whiskey. • Ethanol is composed of two carbon atoms and six hydrogen atoms with one added oxygen atom. FIGURE 11-16 The ethanol molecule showing two carbon atoms, six hydrogen atoms, and one oxygen atom.

48. ALTERNATIVE FUELSEthanol • The majority of the ethanol in the United States is made from: • Corn • Grain • Sorghum • Wheat • Barley • Potatoes

49. ALTERNATIVE FUELSEthanol • Ethanol can be made by the dry mill process in which the starch portion of the corn is fermented into sugar and then distilled into alcohol. • The major steps in the dry mill process include: • Milling. • Liquefaction. • Saccharification. • Fermentation. • Distillation. • Dehydration. • Denaturing.

50. ALTERNATIVE FUELSE85 • E85 is composed of 85% ethanol and 15% gasoline. • Pure ethanol has an octane rating of about 113, whereas E85, which contains 35% oxygen by weight, has an octane rating of about 100 to 105 compared to a regular unleaded gasoline rating of 87.